The invention relates to a process for the production of a liquid package, the tube-shaped side walls of which consist of supporting material, e.g. paper or board, coated with plastic, the bottom of which is quadrangular and produced by folding and sealing and the lid of which, consisting only of plastic and having an opening device, is moulded onto the upper edge of the tube forming the side walls; this involves the coated paper for the tube being drawn off a supply roll in web form, cut into sheets and shaped into the tube, after which the lid is moulded on and the bottom is folded and closed.
The invention also relates to an apparatus for the production of such a liquid package with a supply roll, conveying mechanisms for the paper web, cutting mechanisms for the separation of the web into sheets, tube-shaping mechanisms and conveying mechanisms for the sheets to further work stations.
Liquid packages of the type described at the start are already known. The lid consisting only of plastic may in this case be of quadrangular or round design in cross-section or plan view. In side-view, the lid may be flat like a disc, or else of a design provided with a truncated cone-shaped portion.
In the case of known production processes, the supporting material web, coated at least on one side with plastic, referred to hereafter as paper web, is drawn off a supply roll and fed in this draw-off direction, which is the same as the further conveyance direction, to further work stations, e.g. for cutting, shaping of a tube and closing. It goes without saying that the tube is closed by a longitudinal sealed seam. In the case of the liquid packages which are produced by the known processes, the longitudinal sealed seam, and thus also the longitudinal centre line of the tube lies not only in the general conveyance direction but thus also in the direction of the paper fibres, since generally with a roll the paper fibres always lie in the longitudinal direction of the web. The apparatuses, processes and liquid packages according to the invention which are considered are understood as operating from a roll.
The position of the paper fibres in the longitudinal direction of the tube, i.e. in the direction of the longitudinal sealed seam, makes a package of elongated configuration, in which for example one or two liters of milk are packed, transported and offered to the final consumer, have a certain softness of the side walls, which although not very troublesome or awkward in use, would nevertheless be gladly avoided by the producer.
Furthermore, as well as the constant demand for good tightness of the liquid package, there is always the consideration of edge protection at the longitudinal sealed seam. A paper web can, namely, be shaped into a tube and closed by means of its longitudinal sealed seam in such a way that the two free longitudinal edges of the web are sealed by laying them so that they overlap or inside on inside. The forces occurring due to the filled product are better absorbed by the sealed seam produced by overlapping. In this case, however, a cut edge protrudes inside the package, the plastic coating being severed by the cut or else the supporting material, preferably the paper, being exposed to the filled product at the cut edge. The liquid can penetrate into the paper fibres, soften them and destroy the package. Therefore, a separate strip is laid along the inside of the overlapping sealed seam as edge protection. It goes without saying that the laying on of a special strip is gladly avoided, especially as other sealing strips are also laid on in particularly critical folding regions and the like.
In the case of the other type of sealed seam, in which the strip-shaped ends are joined or sealed to each other inside to inside, the compressive forces of the filled product to the outside can induce an impairment and a breaking open of the sealed seam.
These problems were known to package producers, which is why a butt sealed seam has also already been provided, which is however inconvenient. Furthermore, the liquid package represents a mass product, so that it would be expedient for the producer of the package and also the packing company for the liquid to have high-capacity machines, the capacity of which is above that of conventional machines.